The neuroendocrine regulation of pituitary release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) will be investigated in juvenile and adult pituitary stalk-sectioned, female rhesus monkeys. The effects of chronic episodic infusions of luteinizing hormone-releasing hormone (LHRH) on serum LH and FSH in these animals will be used to assess the hypothalamic and hypophyseal contribution to maintenance of cyclic ovarian activity. After gonadotropin secretion has been re-established in these two models, the feedback actions of estradiol will be studied. Results of these experiments will provide information as to where these feedback actions occur. Chronic electrical stimulation of the ventromedial-arcuate region of the hypothalamus in juvenile rhesus monkeys, animals which have low gonadotropin levels, will be used to elevate gonadotropin levels prematurely by causing the release of endogenous LHRH. Both LHRH infusions and electrical stimulation will be utilized in attempts to stimulate cyclic ovarian activity in primate models where it dose not naturally occur. The studies will indicate whether the feedback actions of estrogen can be elicited from the pituitary in the absence of hypothalamic support and if the hypothalamic-pituitary unit can be driven by electrically induced LHRH release.